It is a time-honored practice in experimental surgery research and teaching that the dog is the laboratory animal of choice. But this practice has been changing over the last fifteen years. As the use of swine increased as the laboratory animal of choice, the use of dogs decreased substantially. Reasons for this decrease in the use of dogs in surgical research and teaching include the following: 1) studies show that the dog is the most liked animal in the United States, and therefore there is a public sentiment against the use of dogs in the laboratory; 2) there is a dwindling availability of dogs in areas where the use of pound dogs in the laboratory has been restricted by legislation; 3) commercial swine can be readily obtained more cheaply than dogs in many areas of the United States; and 4) the physiologic and anatomic structures of swine are more similar to man than dogs.
Other biomedical researchers also have looked to other animal species on which to conduct research. These animal species include, but are not limited to, sheep, goats, miniature swine, rabbits and ferrets. All these animals, when under general anesthesia, require an endotracheal tube.
Placing an endotracheal tube into and down the trachea of an anesthetized animal is very difficult to do by oneself. In the standard two-person technique, a designated assistant opens and retains open an animal's mouth by applying tension on gauze loops over the upper and lower jaws. A second person inserts an endotracheal tube into and down the trachea of the animal. Intubating an animal of any size, whether in ventral or dorsal recumbency, with the two-person technique presents a difficult task.
One known animal mouth retractor works well on dogs. As shown in FIGS. 1 and 2, the known retractor comprises a pair of spaced elongated arms 1 and 2 having holes 3 and 4, respectively, formed therethrough. These holes have a substantially square cross-section at a first end thereof and slidably receive a retainer rod 5 which has a complementary square cross-section. A compression spring 6 surrounds retainer rod 5 and has the opposite ends thereof in engagement with facing surfaces 7 and 8 of the two arms. Opposite ends of the rod are provided with threaded holes (not shown) which receive threaded bolts 9 and 10 therein. Washers 11 and 12 surround the bolts and are positioned between the ends of rod 5 and the heads of the bolts. The bolts and washers prevent the ends of the rod from passing through holes 3 and 4 and maintain spring 6 under compression.
Each of arms 1 and 2 have holes formed through the ends opposite the first ends thereof, which holes receive inserts 13 and 14, respectively. These inserts have holes formed therein for receiving the canine teeth of a dog and are formed of suitable material to prevent damage to the teeth.
The manner in which the retractor works is illustrated in FIG. 2 wherein the upper and lower canine teeth at one side of the dog's mouth are received within the inserts in the arms. The arms are urged apart by spring 6 to hold the jaws of the dog in spaced relationship.
Devices of the aforementioned type have been especially useful in experimental surgery research and teaching conducted on dogs. However, due to the reasons mentioned above, the use of dogs in surgical research and teaching has decreased while the use of swine and other animal species has increased. These other animal species include, but are not limited to, sheep, goats, cats, rabbits and ferrets. Since these alternative animals, unlike the dog, do not possess protruding canine teeth, the prior art mouth retractor shown in FIGS. 1 and 2 cannot be used. A need therefore exists for an animal mouth retractor which can be used on animals that do not possess protruding canine teeth. A need also exists for an animal mouth retractor which can be used on animals of different species and on animals of different sizes having different sized upper and lower jaws.